Pressure converter

ABSTRACT

A pressure converter is disclosed as having an inner cylinder arranged in an outer cylinder and connected to an end piece of the outer cylinder, and in which a large and a small piston are connected to each other so that the large piston can be displaced in the outer cylinder and the small piston can be displaced in the inner cylinder. The inner cylinder is arranged to tilt relative to the outer cylinder in order to permit misalignment of small piston. In this way difficult and costly machining of the outer cylinder is avoided.

e a Unite States 1 1 1111 3,848,4M Larsson Nov. 19, 1974 [54] PRESSURE CONVERTER 3,200,717 8/1965 Einsiedler 92/152 x ,2 19 B d 92 9 X [75] Inventor: Mm R018 Lawson Atvldaberg isiiii $192; l-i isi e d 9 2 /1 18 Sweden 3,314,336 4/1967 Jorgji 92/118 [73] Assignee: Aktieholaget Assa, Atvidaberg,

Sweden Primary Examiner-Irwin C. Cohen Assistant Examiner-Abraham Hershkovitz [22] Filed 1973 Attorney, Agent, or Firm-Anthony A. OBrien [21] Appl. N0.: 332,315

[57] ABSTRACT [30] Foreign Apphcauon Prmmy Data A pressure converter is disclosed as having an inner Feb. 29, Sweden cylinder arranged in an uter cylinder and connected to an end piece of the outer cylinder, and in which a [52] US. Cl 60/593, 92/119, 92/152, large and a small piston are connected to each other 92/164 so that the large piston can be displaced in the outer [51] Int. Cl FlSb 7/00 cylinder and the n piston can be displaced in the [58] F'eld of Search 92/119, 152; inner cylinder. The inner cylinder is arranged to tilt 60/547 593 relative to the outer cylinder in order to permit misalignment of small piston. In this way difficult and [56] References cued costly machining of the outer cylinder is avoided. UNITED STATES PATENTS 9 Cl 2 D F 2,819,935 H1958 Grad 92/164 x rawmg gums PRESSURE CONVERTER The present invention relates to pressure converters in which an inner cylinder is concentrically mounted in an outer cylinder, and is connected to an end piece of the outer cylinder. A large and a small piston are connected to each other such that the large piston can be displaced in the outer cylinder and the small piston can be displaced in the inner cylinder. The inner cylinder is connected to a union in the end piece.

Various pressure converters are already known. Normally the two concentric cylinders are designed to be rigidly coupled to each other. It then becomes extremely important that the cylinders and pistons be manufactured in such a way that, after assembly, they take up a mutually concentric and parallel positions. In such a construction, it is a considerable problem to manufacture the cylinders within tolerance and to assemble them so that they are mutually parallel. If this is not achieved there will be strains between the pistons and cylinders as the pistons move. As a result, the pistons will move sluggishly and unnecessary wear will occur on seals and guides.

In other designs the large piston has a large clearance in an outer cylinder and is sealed to the cylinder with the aid of a diaphragm stretched across it. This diaphragm is subjected to considerable strain in the form of pressure surges. The diaphragm is sensitive to damage and only permits a restricted stroke.

The object of this invention is to produce a pressure converter without the disadvantages set out above and to produce a pressure converter which will be simple and advantageous to manufacture and maintain.

A feature of a pressure converter made in accordance with the invention is that the inner cylinder is permitted to tilt relative to the outer cylinder in order to permit misalignment of the small piston. This avoids the necessity for difficult and costly machining of the end piece and end section of the outer cylinder. It is also possible to use a simpler version of the outer cylinder than was previously the case, for instance commercial tubing such as cold drawn hydraulic tubing may be used. This feature also makes it possible to achieve a long stroke and a high pressure conversion ratio, while at the same time reducing the risk of leakage.

In one embodiment a spigot projecting from the end piece enters some distance into the inner cylinder so as to form the tilting centre of the inner cylinder; the spigot is sealed against the bore of the inner cylinder and connects the inner cylinder to the union via a duct. The spigot, which can form part of the end piece or which can be a separate piece fixed in the end piece in various ways, is simple to manufacture and allows the inner cylinder to easily tilt relative to the end piece.

According to another feature of this embodiment the inner cylinder is retained on the spigot by means of a locking device arranged in the outer cylinder. The chamber in the outer cylinder between the large piston and the end piece is divided into two sections by the inner cylinder, fluid connection being maintained between the two sections by ducts in the inner cylinder. In addition, an aperture in the wall of the outer cylinder, or in the end piece, opens into this chamber. This is to allow the pressure all round the inner cylinder to be the same, so that, since the spigot and the small piston have the same cross-sectional area, the inner cylinder is relieved of displacement forces.

According to yet another feature of this embodiment. part of the inner cylinder has the form of a spherical section, the surface of which is arranged to be in contact with the inner wall of the outer cylinder. and the centre of which is arranged to coincide with the tilting centre of the inner cylinder. Another possibility is to make the largest outside diameter of .the inner cylinder smaller than the inside diameter of the outer cylinder. Depending on the diameter of the outer cylinder, it may be desirable to provide some manner of guide for the inner cylinder.

It is also advantageous to include a spring, preferably a helical spring, to act on the large piston in one of its directions of motion. The strength of this spring can be selected to impose on the large piston a suitable return motion, so that it affects the pressure conversion ratio which is achieved.

The invention is explained below in greater detail with the aid of the examples of its execution shown in the attached drawing, in which:

FIG. 1 shows a longitudinal section through a pressure converter in accordance with the invention, and

FIG. 2 shows a longitudinal section through another execution of the pressure converter.

The pressure converter 1 shown in FIG. 1 is provided with an outer cylinder 2, one end of which is closed off by an end piece 3 screwed in or attached in some other way to the end of the cylinder. The other end of the outer cylinder 2 is provided, in the case shown here, with a sealed end closure 4. A large piston 6 fitted with a seal 5 is housed in the outer cylinder 2 and is displaceable within it. The dimension of piston 6 in the direction of displacement is such that a certain amount of axial misalignment is possible. A small piston 7 with a diameter smaller than that of the large piston 6 is rigidly coupled to the large piston 6 and is displaceable within an inner cylinder 8. Normally the fit of the small piston 7 in the inner cylinder 8 is sufficiently tight to provide a fluid seal, but the seal can be improved, if necessary, by providing one or more seals 9. Disposed in the opposite end of the inner cylinder from the small piston 7 is a spigot 10 projecting essentially centrally from end piece 3. Both the small piston 7 and the inner cylinder 8 are essentially centrally positioned in outer cylinder 2.

Spigot 10 has a partially spherical surface 11 which is a good fit in the inner cylinder and which rests against an annular stop 12 fitted in a recess in the inner cylinder. The inner cylinder 8 can tilt relative to the outer cylinder 2 around the centre 13 of spherical surface II, which is therefore the tilting centre of the inner cylinder. A certain amount of misalignment between the inner cylinder and the small piston is therefore possible without the small piston binding or moving sluggishly in the inner cylinder. Close to the tilting centre 13, spigot 10 is also provided with a seal 14 in a groove.

The inner cylinder 8 is provided with a collar 15, the diameter of which is greater than the diameter of the rest of the inner cylinder. In the example of FIG. 1 the outer surface 16 of collar 15 has the shape of a spherical section with its center at the tilting centre 13, the surface contacting the wall of outer cylinder 2. A retainer l7 fitted to a groove in the outer cylinder abuts the spherical surface 16 to retain the inner cylinder 8 on spigot 10. A chamber 18, bounded by end piece 3 and large piston 6 in outer cylinder 2, is divided by inner cylinder 8 into two sections 19 and 20 connected via one or more ducts 21 in collar 15. This connection can also be achieved by providing the spherical surface 16 with slots so that is is only partially in contact with have the same diameter, inner cylinder 8 is not subjected to any axial forces and can easily tilt around spigot 10. In order to further facilitate the tilting motion, the pressure occurring in chamber 18 from to the motion of large piston 6 can be released via an opening 22 in the outer cylinder. A spring 23, preferably a helical spring, is held compressed between large piston 6 and a spring stop 24 which rests against retainer 17.

A duct 25 in end piece 3 and spigot 10 connects the space in the inner cylinder between the small cylinder and the spigot to a high pressure union 26 fitted in the end piece. A chamber 27 on the opposite side of large piston 6 from chamber 18 is connected to a low pressure union 28.

The embodiment shown in FIG. 2 differs from the pressure converter described above principally in the construction of collar and spigot 10. In this case collar 15 is smaller in diameter than outer cylinder 2, so that inner cylinder 8 is guided only by spigot 10. The connection between chamber sections 19 and is achieved by means of ducts or slots 21 in retainer 17. Here, spigot 10 is in the form of a component fitted into end piece 3 and provided with one or more seals 30. Opening 22 is arranged in end piece 3 instead of in the wall of the outer cylinder 2.

The pressure converter described above may be used for a number of different purposes, for instance to convert a low pressure to a high pressure or vice versa. It can be used for liquid or gaseous media or for conversion from a liquid to a gaseous medium, in which case, for instance, the low pressure union may be connected to a gaseous medium and the high pressure union may be connected to a liquid medium or vice versa. By connecting the low pressure union to a pulsating low pressure source, a pulsating high pressure is obtained in a pipe connected to the high pressure union. The pres sure conversion ratio is determined by the magnitude of the piston areas, by the spring force, and by the pressure in chamber 18. In the normal application of the converter the medium in chamber 18, which may be liquid or gaseous, should not be compressed, and opening 22 should therefore be connected to an expansion vessel (not shown in the drawing) or to the open air.

By connecting in a conventional manner, as via nonreturn valves, a suction and a pressure line to high pres sure union 26, the pressure converter shown may be used to pump a medium under high pressure. Instead of the embodiment shown here it is also possible to arrange for spring 23 to act on the other side of large piston 6, to use opening 22 as a low pressure connection, and to connect the low pressure union 28 to the atmosphere or the equivalent. A system of this type can be used, for instance, for a braking system which is to operate in the event of braking pressure failure, where the braking pressure is used to counteract the spring force when the'brakes are not applied.

The basic idea of the design described above can be used with various modifications for such devices as hydraulic and pneumatic cylinders with long or short strokes, for pumps, brakes, etc. One example of the possible modification is to make large piston 6 a twoway piston and thus eliminate spring 23. End piece 3 the outer cylinder. Since the small piston 7 and spigot 5 could then be sealed off from outer cylinder 2, and low pressure union 28 and opening 22 could be connected to a conventional type of valve system to control the direction of motion of the piston.

What I claim is:

l. A pressure converter comprising an outer housing having an inner cylindrical surface defining a cylindrical cavity through said housing, said inner surface having two ends,

first and second end pieces at each end of said inner surface, said end pieces closing the cavity in said housing, said end pieces each having a fluid union therein,

a first piston disposed in the cavity in said housing toward said first end piece and abutting said inner surface of said housing,

a tubular member disposed in the cavity in said housing toward said second end piece and having an inner cylindrical surface therein defining a cylindrical cavity through said tubular member,

a second smaller piston disposed in the cavity in said tubular member and abutting said inner surface of said tubular member, said second piston being rigidly connected to said first piston, and

a spigot having a rounded outer surface extending from said second end piece into the cavity in said tubular member, and having a fluid connection therein between said cavity and said union is said second end piece, said spigot abutting the inner surface of said tubular member such that it forms the tilting axis of said tubular member which is tiltable relative to said second end piece and said outer housing.

2. A pressure converter as claimed in claim 1 wherein retaining means disposed on the inner surface of said outer housing retains said tubular member on said spigot.

3. A pressure converter as claimed in claim 2 wherein a collar extends radially outward from said tubular means to abut the inner surface of said outer housing, said collar having fluid ducts therein so as to allow fluid communication between all areas of the cavity in said outer housing between said first piston and said second end piece, and wherein an opening in the outer housing allows fluid communication between these areas and the exterior of the housing.

4. A pressure converter as claimed in claim 3 wherein said collar has an outer surface formed as a spherical section and wherein said collar is arranged on said tubular member such that said spigot disposed in the cavity in said tublar member lies at its geometric center.

5. A pressure converter as claimed in claim 4 wherein said retaining means acts on said collar on said tubular member.

6. A pressure converter as claimed in claim 5 wherein a helical spring having two ends is disposed in the cavity in said outer housing such that one end abuts said retaining means and the other end presses against said first piston.

7. A pressure converter as claimed in claim 2 wherein a collar extends radially outward from said tubular member such that said retaining means acts on said collar to retain said tubular member on said spigot and wherein said retaining means has ducts therein to allow fluid flow therethrough.

8.-A pressure converter as claimed in claim 7 wherein said spigot is removably mounted in said second end piece and is fitted with a fluid seal to seal the connection between said spigot and said second end piece.

9. A pressure converter as claimed in claim 8 wherein said second end piece has a duct therein to allow fluid communication between the cavity in said outer housing and the exterior of said outer housing. 

1. A pressure converter comprising an outer housing having an inner cylindrical Surface defining a cylindrical cavity through said housing, said inner surface having two ends, first and second end pieces at each end of said inner surface, said end pieces closing the cavity in said housing, said end pieces each having a fluid union therein, a first piston disposed in the cavity in said housing toward said first end piece and abutting said inner surface of said housing, a tubular member disposed in the cavity in said housing toward said second end piece and having an inner cylindrical surface therein defining a cylindrical cavity through said tubular member, a second smaller piston disposed in the cavity in said tubular member and abutting said inner surface of said tubular member, said second piston being rigidly connected to said first piston, and a spigot having a rounded outer surface extending from said second end piece into the cavity in said tubular member, and having a fluid connection therein between said cavity and said union is said second end piece, said spigot abutting the inner surface of said tubular member such that it forms the tilting axis of said tubular member which is tiltable relative to said second end piece and said outer housing.
 2. A pressure converter as claimed in claim 1 wherein retaining means disposed on the inner surface of said outer housing retains said tubular member on said spigot.
 3. A pressure converter as claimed in claim 2 wherein a collar extends radially outward from said tubular means to abut the inner surface of said outer housing, said collar having fluid ducts therein so as to allow fluid communication between all areas of the cavity in said outer housing between said first piston and said second end piece, and wherein an opening in the outer housing allows fluid communication between these areas and the exterior of the housing.
 4. A pressure converter as claimed in claim 3 wherein said collar has an outer surface formed as a spherical section and wherein said collar is arranged on said tubular member such that said spigot disposed in the cavity in said tublar member lies at its geometric center.
 5. A pressure converter as claimed in claim 4 wherein said retaining means acts on said collar on said tubular member.
 6. A pressure converter as claimed in claim 5 wherein a helical spring having two ends is disposed in the cavity in said outer housing such that one end abuts said retaining means and the other end presses against said first piston.
 7. A pressure converter as claimed in claim 2 wherein a collar extends radially outward from said tubular member such that said retaining means acts on said collar to retain said tubular member on said spigot and wherein said retaining means has ducts therein to allow fluid flow therethrough.
 8. A pressure converter as claimed in claim 7 wherein said spigot is removably mounted in said second end piece and is fitted with a fluid seal to seal the connection between said spigot and said second end piece.
 9. A pressure converter as claimed in claim 8 wherein said second end piece has a duct therein to allow fluid communication between the cavity in said outer housing and the exterior of said outer housing. 